# Lesson: Approximation to Solve Whole Number Computations

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### Lesson Objective

SWBAT select the exact answer or the approximation to solve whole number computations.

### Lesson Plan

Materials Needed: DN worksheet, dry erase markers, white board, pencils, IND Worksheet.
Vocabulary: rounding, estimation, actual, rounding off, decimals, place value, difference, sum

……….
Do Now (5 min): Teacher gives each student a DN worksheet and asks him or her to complete the work as quickly and quietly as possible. DN today is a review of rounding to the hundred millions.

Opening (2 -3 min): Teacher quickly reviews answers to the Do Now and then says, “Yesterday we judged the reasonableness of an answer by using estimation. Today, we going to look at questions we will likely see on our test. By the end of this lesson, you will be able to select the exact answer or the approximation to solve whole number computations.”

Direct Instruction (10 min): Teacher begins “Ok! So today is going to be about our listening skills, because we are going to have to know if we are looking for the actual or an approximate answer. The problem will always tell us be we have to be looking for it as well.” Teacher writes the following on the board:

Taja went to the mall with \$110.97 after his birthday. He spends \$32.04 at the shoe store Then he spent \$45.89 at the game stop.  Approximately how much money does Taja have left to spend?

The teacher reads the problem aloud and then continues, “Ok, what type of answer are they looking for here? [Approximate]. Yes, does that mean that I am going to spend my time finding the actual answer? [NO!] I am going to pick one of my estimation strategies. Who can remind me of our estimation strategies [rounding and regrouping] Thank you! So I am going to use my estimation strategies to find an APPROXIMATE answer.” The teacher then reveals the multiply choice selections.

\$20 \$30 \$50 \$180

“Here are the answer choices, just by looking at ? [You are going to be rounding to the tens place.] Nice work! That is exactly right. The answer choices tell me where I need to round to. Ok, now I am going to work out my problem. Before I do, let’s review what I’ve done already.  1) read the problem carefully 2) decide if it is an approximate or actual answer needed 3) look at the answer choices to get a clue on place I am rounding to. OK! Let’s solve this problem!

110.97 – 32.04 – 45.89 =
Strategy: Rounding to nearest tens
110 – 30 – 50 =
110 – 80 = 30

The answer is choice B!

“Ok, Let’s review what I did before you we do one together.
1) read the problem carefully
2) decide if it is an approximate or actual answer needed
3) look at the answer choices to get a clue on place I am rounding to. OK! Let’s solve this problem!
4) Wrote down the relevant information
5) Rounded each number
6) solved
7) matched my answer to the MC answer choices.”

Guided Practice (5 min): Teacher says, “Now, I will give you one problem to complete in groups of 2 or 3 on your own paper. Help each other as you work, because in a minute I will have you do a problem on your own. Teacher writes the following on the board and gives each student time to solve the problem together in small groups.

Emily had \$58.90. She went to the mall and spend \$41.26 on jeans. Approximately how much money does Emily have left?

A. \$100
B. \$15
C. \$20
D.\$10

(Answer is C)

Independent Practice (5 min): The teacher reviews the answers to the Guided Practice with the class and then passes out the IND practice worksheet.

Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to quickly review the answers to the Independent Practice/ ask what we learned about.

### Lesson Resources

 IND lesson 11 estimation   Classwork DN lesson 11 estimation   Starter / Do Now
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